The invention relates to an intake device for an internal combustion engine which comprises at least two shells welded together at mating joint surfaces.
Intake devices of this type are known from European Patent Application No. EP 568,560, for example. According to this document, an intake device is constructed as a hollow chambered structure made of synthetic resin material, comprising a plurality of shells welded together which form the hollow chambers provided within the structure. These hollow chambers comprise primarily the collection chamber and the intake ducts which branch off therefrom. The intake ducts in intake devices often have a curved design due to the installation conditions and the required flow geometry. In these cases, the partition line which encompasses the mating joint surfaces for the weld also has a curved design.
To weld the shells of the intake device, a joining force is applied which ideally is perpendicular to the alignment of the partition line. A compromise must therefore be made when curved partition lines are present, since the effective joining force provided is diminished for the welding of partition lines which are obliquely inclined to the welding direction. According to EP 568,560, it is possible to achieve an inclination to a plane perpendicular to the direction of the welding force (xe2x80x9cwelding directionxe2x80x9d for short) up to not substantially exceeding 60xc2x0.
Accordingly, the welding direction is most advantageously specified when the curved partition line has a similar angle on both ends with respect to the direction of the welding force. The transverse forces which arise during welding as a result of the inclination of the partition line are thereby compensated for or offset. Frequently, however, as a result of the geometry, it is not possible to orient the pressure force for the welding in the optimum way described above. Specifically, the shells of the intake pipe often have an outer contour which does not allow the welding tool to be applied in the ideal welding direction, thus requiring a deviation therefrom. In this case, disadvantageous transverse forces arise during the welding process which must be compensated for by appropriately dimensioning the welding tools or the welding machine. Designing the equipment to accommodate the high transverse forces thus results in additional costs which adversely affect the economy of the welded intake pipe. In addition, the transverse forces can cause the shells to shift during the welding process, resulting in lowered quality of the welding seam and tolerance problems with the finished parts.
The objects of the invention, therefore, are to provide an intake device for an internal combustion engine which can be welded independent of the external geometry, thereby obtaining an optimal result with regard to the economy and quality of the welding seam.
These and other objects are achieved in accordance with the present invention by providing an intake device for an internal combustion engine, comprising an inlet, cylinder-side outlets for combustion air, and duct structures which form communicating connections between the inlet and the outlets, wherein the duct structures are formed at least partially by at least two shells welded together along a partition line under application of a welding pressure force; the partition line being defined by mating joint surfaces on the shells which at least in partial regions are oriented at an angle of less than 90xc2x0 relative to the welding pressure force; wherein the application of the welding pressure force on the sum of the partial regions generates a first transverse force Q1 relative to the welding pressure force during welding of the intake device, and wherein additional mating surfaces are arranged within the shells which during application of the welding pressure force create a second transverse force Q2 relative to the welding pressure force, the second transverse force Q2 at least partially offsetting the first transverse force.
The invention is based on the principle that at least partial compensation must be made for the transverse forces resulting from the geometry of the partition line and the choice of the welding direction. If this compensation is achieved by forming contacting surfaces which are involved in the welding, the transverse forces can be offset or equalized in the component itself. Thus, the transverse forces are not transmitted to the molds, but instead are intercepted by the component itself. As a result, the welding tools may be designed with smaller dimensions, so that the components may be produced more economically.
In addition, the compensation of transverse forces resulting from the component geometry produces better welding results with respect to quality of the welding seams, since equalization of the transverse forces prevents the two shells to be welded from shifting in the direction of the transverse forces. The described measures also allow the intake devices to satisfy more stringent dimensional tolerance requirements. This further simplifies the installation of the intake pipe on the internal combustion engine, thereby increasing the economy of the proposed solution.
The intake device according to the invention comprises at least two duct structures which connect an inlet for combustion air to cylinder-side outlets in a known manner. The cylinder-side outlets are usually integrated into a cylinder head flange which facilitates installation of the intake device on the internal combustion engine. The inlet generally opens into a collection chamber from which at least one intake duct per cylinder leads to the cylinder-side outlets. The collection chamber therefore serves to distribute the combustion air to the individual cylinders. The described minimum requirements for the geometry of the duct structures can be supplemented by additional functions. For example, longer and shorter intake ducts may be provided which are switched by corresponding valves, depending on the operating mode of the internal combustion engine.
In order to satisfy the complex geometric requirements for the duct structures, the duct structures are formed at least partially from at least two shells which have a partition line along which the shells may be welded together upon application of a pressure force. For this purpose the vibration welding method is particularly useful, in which a high-frequency relative motion between the shells is produced which causes the shells to fuse at joint surfaces which mate with each other along the partition line, thereby joining the shells. Any desired number of individual shells may be combined with one another if adaptations are made for the complexities of the geometry of the intake device.
To form the geometry of the duct structures, the partition line between the shells is configured, in at least partial regions, at an angle of less than 90xc2x0 with respect to the pressure force required for welding. As already mentioned, this results in creation of transverse forces during the welding. The partition line has corresponding joint surfaces in the intake pipe according to the invention. Joint surfaces in the sense of the invention refer to those surfaces that are necessary to join the two shells to one another so that the intake device forms a sealed, hollow chambered structure which can withstand the required bursting pressure. The sum of the partial regions having an angle less than 90xc2x0 with respect to the pressure force results in a first transverse force which is not zero and which is transmitted to the welding tools.
The intake device according to the invention is characterized by the fact that within the shells are arranged corresponding additional surfaces which at least partially compensate for the first transverse force by creating a second transverse force which opposes the first transverse force. Preferably, of course, the first transverse force is completely offset; however, the described advantages of the invention are also obtained to a lesser extent even when the transverse force is only partially offset.
Corresponding additional surfaces in the sense of the invention refer to those surfaces which are not necessary for forming a sealed cavitated structure in the manner previously described, but which instead are provided solely to create the second transverse force. It is understood that these surfaces may take on functions resulting from the construction of the intake pipe. For example, additional partitions may be integrated into the cavitated structure of the intake device. Other possibilities for the design of corresponding additional surfaces are addressed in more detail hereinafter.
According to one advantageous embodiment of the inventive concept, the partition line is designed with a continuous curvature. As a result of this design, there are no abrupt changes in the course of the angle of the partition line for aligning the welding force. Weak points on the welding seam in the walls of the intake device may thus be avoided. In addition, the continuously curved partition lines simplify in particular the production of the intake ducts, which are also advantageously curved.
According to another advantageous embodiment of the invention, the described additional surfaces may comprise a widening of the joint surfaces. Widening of the joint surfaces is provided, for example, on the side of the curved joint line which creates the smaller transverse force with respect to the welding direction. This results in equalization of the transverse forces, in which the total sum of the first transverse forces offsets the total sum of the second transverse forces.
Widening of the joint surface refers to an enlargement of the joint surface by an amount which is not necessary to create a secure connection between the shells of the intake device. In the sense of the invention, the entire width of the welding bead provided in the partition line is thus created from the joint surface, which has a minimum width for creating the secure connection, and an additional surface extending on the other side of this joint surface, level with the widening of the joint surface.
The described design advantageously represents an elegant variant for accommodating the joint surfaces in the intake pipe. These joint surfaces disappear in the welding catching edge formed by the partition line, so that the intake pipe according to the invention does not differ in appearance from the intake pipes of the prior art. Finally, the wider welding edge may also provide the intake pipe with increased strength.
A further advantageous embodiment of the invention envisions that the corresponding additional surfaces are provided inside the shells. This has the considerable advantage that the demands for seal-tightness placed on the joined additional surfaces are significantly less than those placed on the joint surfaces on the walls of the intake device. The structures which have the corresponding additional surfaces may also perform other functions in the intake pipe. For example, these structures may form partitions which conduct the intake air flow or improve the acoustics of the intake noise. Furthermore, after the intake pipe is welded, the additional surfaces can no longer be detected from the outside, so that the appearance of the intake device is not impaired.
A further advantageous variant of the intake pipe provides that the corresponding additional surfaces are integrated into mountings or connection points for attaching the intake device or additional units. Such connection points are externally attached to the intake device and may comprise, for example, mounting flanges. Additional units that could be attached to these connection points include, for example, fuel injection nozzles or a servomotor for switch valves in the intake pipe. Furthermore, the intake device must be mounted in the engine compartment, which can be externally accomplished via the cylinder head flange or other connection points. Use of resilient or elastic connecting elements, for example, can achieve a vibration damping effect.
The incorporation of the additional surfaces into the connection points has the advantage that no additional materials are required as the result of providing the additional surfaces. In addition, the connection points may be advantageously disposed in the vicinity of the partition line, thereby facilitating ejection of the shells of the intake device from their respective casting molds.
In accordance with a further advantageous embodiment of the invention, the additional surfaces are inclined so greatly that their angles xcex1 relative to pressure force D are less than 24xc2x0. As a result, the additional surfaces produce a large transverse force in relation to their area. The problems that can arise from reduced welding seam quality as a result of the lower effective welding force can be eliminated, in particular by providing the additional surfaces in the interior of the intake device, since the pressure differences inside the intake device are significantly lower compared to the surrounding environment.
These and other features of preferred embodiments of the invention, in addition to being set forth in the claims, are also disclosed in the specification and/or the drawings, and the individual features each may be implemented in embodiments of the invention either alone or in the form of subcombinations of two or more features and can be applied to other fields of use and may constitute advantageous, separately protectable constructions for which protection is also claimed.